The effects of food abundance, foraging rules and cognitive abilities on local animal movements

by (Jorie Marie). Favreau, Jorie M.

Abstract (Summary)

FAVREAU, JORIE M. The effects of food abundance, foraging rules and cognitive
abilities on local animal movements. (Under the direction of Roger A. Powell.)
Movement is nearly universal in the animal kingdom. Movements of animals
influence not only themselves but also plant communities through processes such as seed
dispersal, pollination, and herbivory. Understanding movement ecology is important for
conserving biodiversity and predicting the spread of diseases and invasive species.
Three factors influence nearly all movement. First, most animals move to find
food. Thus, foraging dictates, in part, when and where to move. Second, animals must
move by some rule even if the rule is “move at random.” Third, animals’ cognitive
capabilities affect movement; even bees incorporate past experience into foraging.
Although other factors such as competition and predation may affect movement, these
three factors are the most basic to all movement. I simulated animal movement on
landscapes with variable patch richness (amounts of food per food patch), patch density
(number of patches), and variable spatial distributions of food patches. From the results
of my simulations, I formulated hypotheses about the effects of food abundance on
animal movement in nature. I also resolved the apparent paradox of real animals’
movements sometimes correlating positively and sometimes negatively with food
abundance. I simulated variable foraging rules belonging to 3 different classes of rules
(when to move, where to move, and the scale at which to assess the landscape).
Simulating foraging rules demonstrated that variations in richness and density tend to
have the same effects on movements, regardless of foraging rules. Still, foraging rules
affect the absolute distance and frequency of movements. In my third set of simulations,
I simulated a range of spatial and temporal cognitive constraints and demonstrated that
omniscience is not necessarily the optimal cognitive state from an energetic standpoint.
I tested my hypotheses on the effects of food abundance with data from free
ranging female black bears (Ursus americanus) in Pisgah Bear Sanctuary (North
Carolina, USA) and female kinkajous (Potos flavus) in Parque Nacional Soberanía
(Panama), two species with low predation risk. Depending on the season, black bear
movements can be explained, by food patch richness, density or both richness and
density. Female kinkajou move length correlated positively with patch richness and
density. The number of moves of female kinkajous correlated negatively with patch
richness of all foods that kinkajous eat and selectivity. In contrast, food patch richness
and density did not affect male kinkajous’ moves (length and number). Instead, male
kinkajous increased foraging time on all foods that they eat as patch density decreased.
Male kinkajous also decreased their selectivity on subsets of foods that they eat as patch
richness increased.
My results are broadly interesting because they demonstrate that the success of
the habitat productivity hypotheses depends on how food is measured (patch richness or
density), sex, species, and foraging and non-foraging behaviors (foraging selectivity,
responses to moonlight).